Since 1900, and for census purposes shortly before, the year portion of calendar dates has been truncated to two digits ("55" instead of "1955," for example). The precedence helped maximize the amount of information encoded on 80-column punch cards in use throughout the first half of the 20th century. Such cards were indispensable for the decennial census (1890, 1900, 1910, 1920, 1930, 1940), significantly speeding census counts and post-census count analysis. Without such punch card technology, according to the U.S. government, the 1890 census would not have been completed before the 1900 census began. The machines that processed the cards were called tabulators, later having plug-in boards that could be wired to perform various computational and printed report functions. The same technology gained wide-scale commercial acceptance in business (in addition to census applications) after 1913, maintaining the same two-digit census precedence for the year portion of dates.
By the 1950's, electronic computers began replacing tabulators to support census and commercial data processing. Data storage advances included magnetic tape (herein mag tape") and electromagnetic disk drives (herein "disk drives"). Vast amounts of data originally stored on punch cards were transferred to the new media of mag tape and disk drives. These new storage devices added the ability to randomly and electronically access files through stored program machines, a dramatic improvement over the manual handling of millions of punch cards. The new storage technology also used less physical space to store data than punch cards, as well as obviating much of the labor expense to manually process punch card-based data files.
The two-digit precedence for year portions of calendar dates (instead of four digits) was also used with the newer electronic computers and their storage devices. This simplified the transfer of volumes of punch card data while avoiding additional expense to store four-digit year fields. In doing so, the punch card images were transferred unaltered to the new storage devices, speeding conversion and removing up to an additional 2.5% storage-expense per record. Thus, the two-digit year precedence helped save space and reduce costs when converting to newer storage technology at mid-century. Such technology enabled database files to be accessed randomly instead of only sequentially.
To have done otherwise, such as converting to four-digit years, may have inflated the already high cost of newer storage offerings as compared to punch card technology and its media. No manufacturers desired to include in a product proposal a 2.5% higher cost, which might give competitors an instant 2.5% price advantage who stayed with two digit years already on punch cards. Thus, the remedy (of staying with two digit years) was technologically expedient and helped reduce a price objection by customers, mating the storage devices appear as seamless extensions of proven punch card protocols. This expediency, and its widespread perpetuation during the last four decades, helped set the worldwide conditions for the Year 2000 Malfunction.
None of the computing technology advances since then have reversed the long-term effects of maintaining the two-digit year precedence. Though the cost of disk drive storage has dropped dramatically in the last few decades, the reprogramming expense to reverse out the two-digit date limitation has reciprocally increased each year. New functions were incrementally added to existing programs decade after decade. Such software changes were stimulated by regulatory requirements, new tax reporting and accounting methods, corporate acquisitions, new telecommunications links between multiple computer sites, new hardware and other reasons.
With each and every change, the two-digit year precedence spread like yeast within a batch of dough. Every year, it seemed easier to justify avoiding radical changes to production software that had taken years to develop and stabilize. Leaving software the same as it was the year before, even if the hardware was changed, seemed operationally and fiscally prudent. In numerous cases, this reasoning was followed until the Year 2000 Malfunction began to tangibly manifest itself in economically damaging ways over the past 18 to 24 months.
Current solutions to retroactively address the Year 2000 Malfunction involve restructuring such databases, and rewriting support programs to accommodate full four digit representations of calendar years instead of two digit abbreviations. This reengineering task involves multiple billions of lines of code, and multiple trillions of bytes of data spread throughout government, academic and private sector databases. All of this is running on a host of different computing platforms built during the last 40 years, some of which may no longer be commercially produced, if the manufacturers remain in business at all. Also, due to age, some of the source code for programs in many production systems may no longer be available.
Conventional tools to address the Year 2000 Malfunction may not produce useful results sooner than 18 to 36 months. In many cases, this may make a plethora of systems that electronically handle multiple trillions of dollars of resources--including airline reservations, banking transactions, accounting systems, utilities, government tax collections, social services, and others--inoperable as the frequency of Year 2000 Malfunctions increases.
A more promising and useful solution to the above malfunction has been proposed and described in a prior art U.S. Pat. No. 5,600,836 to Alter. In the Alter implementation, a computing system is configured to operate in "zone" time, which time is different from an external "local" time. The "zone" time is intentionally set at some multiple of four years (preferably 56 years to preserve leap year and day of the week integrity) in the past. In this way, the system perceives that it is operating at a time some 56 years in the past, and therefore, a date operation involving years 2002 and 1985, for example a subtraction operation, is treated as an operation involving years 1946 and 1929 instead. In other words, a conventional un-treated computing system limited to two digit date fields would treat the subtraction operation as 02-85 (the truncated values of 2002 and 1985) and give an erroneous result of -83, but the Alter approach yields the correct result of 46-29=17. By confining the computing system to operate with date field values within a single century, any internal date operations are kept accurate (in a relative sense). To maintain consistency with the outside world, an interface is used in Alter for converting date field data to local or zone time.
Some limitations of the Alter approach, however, include the fact that there is no mechanism for handling databases that include date field data exceeding 100 years in scope. For example, as of 1994 at least, the social security database includes data for birth years for more than 117 years worth of individuals. This cannot be accommodated even in a system modified by Alter, as such is still limited to a single two-digit database structure. Moreover, Alter apparently fails to appreciate that the number of computer programs that can be kept on a system utilizing such approach is limited unless such programs are also "synchronized" with the time adjusted data in such system.